1. Field of the Invention
The present invention relates to a battery, and more particularly to a rechargeable-battery case.
2. Description of the Related Art
A conventional polymer lithium-ion battery 10 is shown in FIGS. 1A, 1B, and 2. The conventional polymer lithium ion battery 10 includes a case 11 for accommodating an electrode assembly 15. As shown in FIG. 1B, the electrode assembly includes positive electrode sheets 12, negative electrode sheets 13 and separators 14 interposed therebetween. The case 11 includes an upper case body 11a and a lower case body 11b having the same shape. Each of the positive and negative electrode sheets is electrically coupled to a connector 16. The connector 16 is further coupled to an external terminal 18 which is drawn out from the case 11 in an extended manner between the upper and lower case bodies 11a and 11b before they are hermetically sealed at their peripheries by a thermal pressing process. The peripheral surfaces, coated with a heat-activated adhesive, of the upper and lower case bodies 11a and 11b are contacted and pressed to hermetically seal the electrode assembly 15 inside the case 11 with the terminals 18 placed between the peripheral edges. However, since the external terminals 18 have a certain thickness, it is probable that peripheral surfaces just around the terminals 18 are not airtightly adhered. In other words, there will exist gaps, though possibly very small, around the terminals 18 between the upper case body 11a and the lower case body 11b. If the electrolyte inside the case 11 should leak out from around the terminals 18, both the battery 10 and a device in which the battery 10 is installed may be damaged.
To solve the above problem, it is an objective of the present invention to seal a battery case. The case is comprised of two portions, each portion having a centrally recessed region to receive an electrode assembly where the depth of the recess is about one half the thickness of the electrode assembly and a peripheral region as the seal surface with a corresponding region of the other portion. Each portion is made of aluminum coated with an insulating material. Rather than providing separate positive and negative terminals electrically coupled to the positive electrodes and negative electrodes, respectively, the battery case itself serves as terminals by electrically connecting the inner surfaces to the electrode sheets and some outer surface portions are made free of an insulating material so that they would function as terminals to which corresponding terminals of a device contact.
A second objective of the present invention is to minimize the size of the battery, which is achieved automatically since the terminals are not necessary in the present invention, unlike in the prior art.